\documentclass{book}
\usepackage{array}

\begin{document}    
\begin{center}
\setlength\extrarowheight{5pt}
\makebox[0pt]{%
\begin{tabular}{ |>{\arraybackslash}m{1in} | >{\centering\arraybackslash}m{1in} | >{\centering\arraybackslash}m{1in} | >{\centering\arraybackslash}m{1in} | >{\centering\arraybackslash}m{1in} | @{}m{0pt}@{}}
\cline{2-5}
 \multicolumn{1}{c|}{}& \multicolumn{2}{c|} {Probe} & \multicolumn{2}{c|} {Probe} \\[0.4cm]
\cline{2-5}
\multicolumn{1}{c|}{} & \multicolumn{1}{c|}{Pump} & \multicolumn{1}{c|} {Pump} & \multicolumn{1}{c|} {Pump} & \multicolumn{1}{c|} {Pump} \\[0.4cm]
\hline
a   & 5,0441    &1,9797 &4,6986 &2,9247   &\\[0.4cm]
\hline
b       &1,0364 &1,0047 &-1,2025    &-0,9834 &\\[0.4cm]
\hline
c   & 0,5283    &0,0717 &0,1125 &0,3644 &\\[0.4cm]
\hline
d   & 0,2361    &0,1967 &-0,1241    &-0,3231 &\\[0.4cm]
\hline
e   & 0,0241    &-0,0014    &0,0028 &0,0286 &\\[0.4cm]
\hline
f       & 0,0924    &-0,0234    &-0,1167    &-0,1930 &\\[0.4cm]
\hline
\end{tabular}}
\end{center}

\hrule

\end{document}
